Add license notice generator

[m4pl]

Adds a script that generates assets/licenses.html, the open-source notices screen shown in the app.
The script itself was written with AI assistance.

How it works

1. Capture the runtime dependency tree once:

./gradlew :app:dependencies --configuration releaseRuntimeClasspath

scripts/license/cache/deps.txt

2. Generate the HTML:

python3 scripts/license/generate_licenses.py --offline

For each dependency the script:

• reads the LICENSE/NOTICE embedded in the .jar/.aar if present
• otherwise falls back to the canonical SPDX text bundled under scripts/license/texts/
• pulls the project name and upstream URL from the POM for attribution

Results are cached per coordinate, so reruns are instant unless versions change.

Release blockers the script enforces

• GPL / AGPL: hard fail, HTML is not written
• LGPL / MPL / EPL / CDDL: a SOURCE AVAILABILITY section is emitted listing upstream URLs
• MIT / BSD / ISC without a real copyright line: CHECK COPYRIGHT section; resolve by adding an entry in scripts/license/license-overrides.json

Output

assets/licenses.html: a single self-contained file, Material 3 styling, each notice collapsed by default, no JS, viewport-fit so there is no horizontal scroll in the in-app WebView.